Hot gas engine with finned cylinder head



June 19, 1951 LUBBOCK ETAL 2,557,607

HOT GAS ENGINE WITH FINNED CYLINDER HEAD I Filed March 29, 1949 2Sheets-Sheet 1 lnvenbrs: isaac L l bbock Vflliam \p\er bq dad/6 mm theirAfiomeu.

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June 19, 1951 LUBBOCK ETAL 2,557,507

HOT GAS ENGINE WITH 'FINNED CYLINDER HEAD 1 Filed Mrch 29, 1949 Y 2Sheets-Sheet 2 \hveri'k'or'ilsaac Lubbock \Vflliarn 'Fpler TheirAH'orneL;

Patented June 19, 1951.

HOT GAS ENGHVE WITH FINNED CYLINDER HEAD Isaac Lubbock and William'llpler, London, England, asdg'nors to Shell Development Company, SanFrancisco, Calif a corporation of Delaware Application March 29, 1949,Serial No. 84,152

In Great Britain March 30, 1948 8 Claims. (CI. 60-24) This inventionrelates to reciprocating engines of the kind in which a. working gas isheated by gaseous combustion products generated externally to theworking cylinder in a combustion chamber open to the cylinder head, thecombustion products being maintained separate from the working gas,which latter is admitted to and/or ejected from the cylinder throughports adjacent to the cylinder head. Examples of engines of this kindare hot gas engines of certain constructions workin on the Stirlingcycle.

In engines of the aforesaid kind, the temperature of the working gas atthe hot end of the working cycle must be of a high order if the thermalefficiency is to compete with that, for example, of internal combustionengines. In order that the working gas may attain the required hightemperature, it is necessary for the temperature in the combustionchamber to be something in excess of l,000 C. Since the cylinder head isexposed to the temperature prevailing in the combustion chamber, thedifiiculty of protect ng the head is a seriouagne especially as thecylinderis subject to stress iiwing to the pressure of the wcrking gas.it has been proposed to fit a cap of refractory material to the externalface of the cylinder head, that is, the face exposed to the combustioncham-; her, but this has the drawback that the cap is difiicult to fitand, when fitted, has poor resistance to mechanical and thermal shock.Moreover, the refractory material is liable to disintegrate, and theresultin particles obstruct the labyrinthine elements through which thecombustion gases pass in order to heat the working gas.

The present invention afiords a practicable and efficient method ofcooling a metal cylinder head in an engine of the aforesaid kind, byproviding the interior face of the head with a plurality of passages orchannels, and by so arranging the aforesaid ports in relation to thesepassages or channels that the wcrking gas entering and/or leaving thecylinder is constrained to flow thr ugh the said passages or channels.By this means the working gas, which, although it is at the hot end ofits cycle, has a temperature much below that of the combustion chamber,maintains the cylinder head at a sufiiciently low temperature. At thesame time, the temperature of the wcrking gas is raised, thus increasingthe emciency of the cycle.

The passages or channels and ports may both be formed or defined by aseries of radial fins projecting from the interior face of the cylinderIn order to minimize this difliculty,

2 cf the centre of the head so as to leave a circular central gap. Thepiston head then has a projecting portion which enters this central gap,so that as the piston moves towards the cylinder head it forces theworking gas from the gap out through the passages or channels betweenthe fins, and vice versa. The interior face of the cylinder head at thecentral gap may advantageously have the general form of a coneprojecting into the cylinder, the base of the cone merging in a smoothcurve into the main part of the cylinder head, and the projectingportion of the piston head having a corresponding conical depression, so

that gas passing into and out of the passages or channels sweeps overthe surface of the cone and aids in the coclirm of the central part ofthe cylinder head.

Instead of passages defined by a series of fins, th aforesaid passagesmay consist of a large number of fine bores or channels in the cylinderhead, each communicating with the cylinder and with the cylinder portsso as to provide cooling for the cylinder head by the working medium.Alternatively the cylinder head may be fabricated from a system of finepipes, so arranged as to be cooled by the working medium flowing intoand out of the cylinder.

If desired, the cylinder head may be provided both with a system of finsand with a series of fine bores or channels.

The'invention is illustrated by way of example by the accompanyingdrawings, in which Figure I is a lcngitudinal section through onecylinder of a multi-cylinder hot gas engine working on the Stirlingcycle; I

Figure II is a section on the line 11-11 of Figure I drawn to anenlarged scale; and

Figure 111 is a further enlarged section developed on a circumferentialsection line indicated at IIIIII of Figure I.

Referring to Figure I, each cylinder I of the engine (one cylinder onlybeing shown in the drawings) is provided with a. combustion chamber 2arranged directly above the cylinder head 3. A burner 4 and igniter 5are inserted in the combustion chamber, which is constructed of a metalwall 6 with a refractory lining l.

The products of combustion generated in the chamber 2 pass into spaces 9between fins 8 which are arranged in sectors round the upper part of thecylinder l. Alternating with the fins 8 are radial pockets in defined byvertical partition walls lllb that extend upwards to the walls 23.

These partition walls have vertical fins I 0a on the head in an axialdirection, the fins stopping short on interior surfaces thereof (facingthe pockets I0) 3 as best shown in Figure II, and these fins extend fromthe bottoms of the walls lllb almost to the upper ends thereof. Asdescribed below, the

pockets ll provide a path for the working gas (usually air) separatefrom that of the combustion products. The latter pass from the spaces 9to a preheater ii for preheating the air for combustion, and are thenexhausted to atmosphere through a duct i2. The air for combustion entersfrom atmosphere through a duct l3 and passes by way of the preheater iito a cooling jacket [5 between the wall 6 of the combustion chamber andthe refractory wall ll of the preheater ii, and thence into thecombustion chamber 2. An air bleed it from the duct i3 serves to coolthe burner l and prevent carbon deposition. The preheater ii consists ofa metal sheet having corrugations running parallel to the axis of thecombustion chamber, the exhaust gas and combustion air ducts being soarranged that these gases pass through the corrugations on oppositesides of the metal sheet.

Surrounding the cylinder i below the pockets I0 is a' regenerator l9,and below this regenerator is a tubular cooler 20. The arrangement issuch that the working gas can pass freely through the tubes of thecooler 2|, the regenerator I9, and the pockets l0, and thence into theupper or hot end of the cylinder i. The exteriors of the cooling tubesare cooled by a fluid (for example water) circulated by a pump (notshown) from a tank 2 l.

The cylinder i contains a piston I1, and the space l8 at the cold end ofthe cylinder below the piston communicates with the cooling tubes of thesecond cylinder of the engine, that shown in Figure I being regarded asthe first. Likewise the space i8 of the second cylinder communicateswith the cooling tubes of the third cylinder and so on, the space it ofthe last cylinder communicating with the cooling tubes of the first. Thecommunication between the spaces is of the several cylinders and theinteriors of the appropriate cooling tubes is efiected by way of headers29 and ducts Iii.

The pistons are so phased that the working gas contained in the spaceit! of one cylinder is alternately caused to fiow from this spacethrough the cooler, regenerator and hollow fins of the next cylinderinto the space above the piston of that cylinder, and then to nowthrough the same path in reverse direction back into the space is. Thephasing is such that the gas in each cylinder performs the Stirlingcycle or a cycle approximating thereto.

The top walls 23 of the pockets ill form extensions of the cylinder head3, and the upper end of the cylinder wall is turned inward to form anannular lip 2. Above this lip is a space communicating freely with theupper ends of the pockets it to which the fins Iva do not extend. Aseries of radial fins 25 extends from the cylinder I head 3 to the lip24, and in between these fins a second series of fins 22 project fromthe cylinder head as illustrated further in Figure III. Thus the workinggas, on passing from the pockets iii into the hot end of the cylinder I,or vice versa, flows through the passages 26 formed between the two setsof fins 22 and 25, and thus cools the cylinder head. The fins 22 arestreamlined and the fins 25 are triangular in cross-section, so that thepassages 26 afford the minimum resistance to the flow of gas. V

The fins 22 and 25 Stop short of the centre of the cylinder, leaving acentral circular gap, and the piston i I has a projecting portion 21which enters this gap when the piston is at top dead centre, thusforcing the working gas from the gap out through the passages 25. Inorder to assist in the cooling of the central part of the cylinder headwhere the cooling fins do not extend the head is formed with a conicalinternal projection 28 which fits a corresponding depression in the part21 of the piston. The base of the projection 28 merges, as shown, intothe main part of the head 3, so as to aid the flow of the working gas.

The invention claimed is:

1. In a hot gas engine of the type having a reciprocating piston withinan engine cylinder in which a working gas is heated by gaseouscombustion products generated in a combustion chamber externally to theengine cylinder, the combustion products being maintained separate fromthe working gas, the combination of: a cylinder head for said enginecylinder having the outer face thereof exposed to the interior of saidcombustion chamber and an inner face thereof exposed to and directedtoward said piston; duct means for said working gas terminating in aplurality of ports located peripherally about the engine cylinder andnear said cylinder head; and a plurality of fins extending from saidinterior face of the cylinder head providing therebetwcen a plurality ofrestricted passages extending from the periphery of the cylinder headtoward the central part of said face, said passages being registeredwith said ports so that working gas entering or leaving the enginecylinder through said ports is constrained to flow through the pasagesfor abstracting heat from the cylinder head.

2. The combination according to claim 1 wherein said fins and passagesextend substantially radially.

3. The combination according to claim 1 wherein said fins and passagesstop short of the center of the cylinder head so as to leave a centralgap and the piston head has a projection toward the cylinder head shapedto enter said gap when the piston approaches the cylinder head.

4. The combination according to claim 3 wherein the part of saidinterior face of the cylinder head at said gap has the general shape ofa cone extending into the engine cylinder and the projection on thepiston which enters the gap has a corresponding generally conicaldepression.

5. The combination according to claim 3 wherein the said interior faceof the cylinder head is generally cone shaped and concave toward theengine cylinder, the part of said interior face at said gap has thegeneral shape of a smaller cone extending into the engine cylinder, andthe projection on the piston which enters the gap has a correspondinggenerally conical depression.

6. In a hot gas engine of the type having a reciprocating piston withinan engine cylinder in which a working gas is heated by gaseouscombustion products generated in a combustion chamber externally to theengine cylinder, the combustion products being maintained separate fromthe working gas, the combination of a cylinder head for said enginecylinder having the outer face thereof exposed to and directed towardsaid piston; duct means for said working gas terminating in a pluralityof ports located peripherally about the engine cylinder and near saidcylinder head; and wall structure on said interior face of the cylinderhead providing a plurality of substantially radial, restricted passages,said passages being in registry'with said ports at their radially outerends and in communication with the interior of the engine cylinder attheir radially inner ends, whereby working gas entering or leaving theengine cylinder through said ports is constrained to flow through thepassages for abstracting heat from the cylinder head.

'7. The combination according to claim 6 wherein the Wall structurecomprises a first set of radial fins extending axially from saidinterior face of the cylinder head and extending radially outwardly tothe periphery of the cylinder head, said fins being located to liebetween adjacent ports and a second set of radial fins extending axiallyfrom said interior face and alternating with the fins of the first set,said second set of fins stopping short of the periphery of the cylinderhead.

The combination according to claim 6 wherein the cylinder is providedwith an annular, peripheral lip spaced axially from said interior faceof the cylinder head so that said ports lie between the cylinder headand the said lip, and the wall structure comprises a first set of radialfins extending axially from said interior face 01 the cylinder to saidlip and extending radially REFERENCES CITED The following references areof record in the file of this patent:

UNITED STATES PATENTS Number Name Date 324,061 Woodbury et a1. Aug. 11,1885 FOREIGN PATENTS Number Country Date 34,036 Germany Dec. 23, 188592,720 Germany July 24, 1897 501,017 France Jan, 14, 1920

